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Abstract:

International Mobile Telecommunications (IMT) Advanced technology, also
known as 4th Generation (4G) targets to support up to 100 MHz BW. LTE
currently supports single carrier bandwidths of up to 20 MHz. The present
application describes a multi-carrier approach in which some embodiments
of the invention provide a simple solution of aggregating multiple single
carrier bandwidths to obtain a wider bandwidth (>20 MHz). Such an
approach may extend Long Term Evolution (LTE) bandwidth to greater than
that provided by a single carrier, yet maintain full backward
compatibility with technologies that predate 4G technology and utilize
smaller, single carrier bandwidths. More generally, embodiments of the
invention can apply to other communication standards than only LTE.

Claims:

1. A method comprising: for a communication link between a base station
and at least one relay station with which the base station is
communicating, allocating a first frequency sub-band; for a communication
link between the base station and a first subset of one or more mobile
stations with which the base station is communicating, allocating a
second frequency sub-band; for a communication link between the at least
one relay station and a second subset of one or more mobile stations with
which the at least one relay station is communicating, allocating a third
frequency sub-band; the at least one relay station performing at least
one of: receiving signals on the first frequency sub-band and
transmitting signals on the third frequency sub-band simultaneously; and
transmitting signals on the first frequency sub-band and receiving
signals on the third frequency sub-band simultaneously; wherein the
first, second and third frequency sub-bands are aggregate non-overlapping
sub-bands that collectively provide increased bandwidth.

2. The method of claim 1, wherein one or more of the first, second and
third frequency sub-band include first, second and third carrier
frequencies, respectively.

3. The method of claim 2 wherein one or more of the first, second and
third carrier frequencies are non-contiguous carrier frequencies within
the aggregate increased bandwidth.

4. The method of claim 1 wherein the first, second and third frequency
sub-bands are contiguous sub-bands within the aggregate increased
bandwidth.

5. The method of claim 1 wherein: allocating the first frequency sub-band
comprises allocating in a down link (DL) frequency band a first DL
frequency sub-band and in an up link (UL) frequency band a first UL
frequency sub-band; allocating the second frequency sub-band comprises
allocating in the DL frequency band a second DL frequency sub-band and in
the UL frequency band a second UL frequency sub-band; allocating the
third frequency sub-band comprises allocating in the DL frequency band a
third DL frequency sub-band and in the UL frequency band a third UL
frequency sub-band; the at least one relay station performing one or more
of receiving signals on the first DL frequency sub-band, transmitting
signals on the third DL frequency sub-band, transmitting signals on the
first UL frequency sub-band and receiving signals on the third UL
frequency sub-band simultaneously in a same time slot.

6. The method of claim 1 wherein: in a first time slot for down link (DL)
communications, allocating in a frequency band the first frequency
sub-band, the second frequency sub-band and the third frequency sub-band;
in a second time slot for up link (UL) communications, allocating in the
frequency band the first frequency sub-band, the second frequency
sub-band and the third frequency sub-band; the at least one relay station
performing: receiving signals on the first frequency sub-band and
transmitting signals on the third frequency sub-band simultaneously
during the first time slot; and transmitting signals on the first
frequency sub-band and receiving signals on the third frequency sub-band
simultaneously in the second time slot.

7. The method of claim 1 further comprising at least one of: a) i)
allocating the first frequency sub-band comprises allocating a dedicated
sub-band; and ii) allocating the third frequency sub-band comprises
allocating a dedicated sub-band; b) dynamically assigning at least one of
the first and third sub-band to a different sub-band than the dedicated
first or third frequency sub-band, respectively; c) changing the size of
the sub-band of at least one of the first, second and third frequency
sub-bands; d) changing the number of carriers included in at least one of
the first, second and third carriers; and e) applying transmission power
distribution control to reduce the interference between transmissions and
receptions of the relay station.

8.-10. (canceled)

11. The method of claim 1, wherein the first, second and third frequency
sub-bands are each greater than 10 MHz and less than 30 MHz.

12. The method of claim 1 wherein the relay station is an LTE enabled
relay station.

13. The method of claim 12 wherein the LTE enabled relay station is
configured to support legacy mobile stations.

14. (canceled)

15. The method of claim 7 wherein applying transmission power
distribution control comprises: transmitting signals on the first or
third frequency sub-bands using a narrow band signal with a higher power
than a wide band signal having a lower power, to reduce to the size of a
guard band between transmissions and receptions of the relay station.

16. A relay station comprising: at least one antenna; transmit circuitry
coupled to the at least one antenna configured to transmit a signal;
receive circuitry coupled to the at least one antenna configured to
receive a signal; relay circuitry configured to: for a communication link
between a base station with which the relay station is communicating and
the relay station, allocate a first frequency sub-band; for a
communication link between the relay station and a set of one or more
mobile stations with which the relay station is communicating, allocate a
second frequency sub-band; the relay station configured to perform at
least one of: receive signals on the first frequency sub-band and
transmit signals on the second frequency sub-band simultaneously; and
transmit signals on the first frequency sub-band and receive signals on
the second frequency sub-band simultaneously; wherein the first and
second frequency sub-bands are aggregate non-overlapping sub-bands that
collectively provide increased bandwidth in conjunction with a third
frequency sub-band for a communication link between the base station and
a second set of one or more mobile stations with which the base station
is communicating.

17. The relay station of claim 16, wherein one or more of the first,
second and third frequency sub-band include first, second and third
carrier frequencies, respectively.

18. The relay station of claim 17 wherein one or more of the first,
second and third carrier frequencies are non-contiguous carrier
frequencies within the aggregate increased bandwidth.

19. The relay station of claim 16 wherein the first, second and third
frequency sub-bands are contiguous sub-bands within the aggregate
increased bandwidth.

20. The relay station of claim 16, the relay station further configured
to: allocate in a down link (DL) frequency band a first DL frequency
sub-band and in an up link (UL) frequency band a first UL frequency
sub-band; allocate in the DL frequency band a second DL frequency
sub-band and in the UL frequency band a second UL frequency sub-band; the
relay station configured to perform one or more of: receive signals on
the first DL frequency sub-band, transmit signals on the second DL
frequency sub-band, transmit signals on the first UL frequency sub-band
and receive signals on the second UL frequency sub-band simultaneously in
a same time slot.

21. The relay station of claim 16, the relay station further configured
to: in a first time slot for down link (DL) communications, allocate in a
frequency band the first frequency sub-band and the second frequency
sub-band; in a second time slot for up link (UL) communications, allocate
in the frequency band the first frequency sub-band and the second
frequency sub-band; the relay station configured to perform: receive
signals on the first frequency sub-band and transmit signals on the
second frequency sub-band simultaneously during the first time slot,
transmit signals on the first frequency sub-band and receive signals on
the second frequency sub-band simultaneously in the second time slot.

22. The relay station of claim 16, the relay station further configured
to: a) i) allocate the first frequency sub-band as a dedicated sub-band;
and ii) allocate the second frequency sub-band as a dedicated sub-band;
b) dynamically assign at least one of the first and second frequency
sub-bands to a different sub-band than the dedicated first or second
frequency sub-band, respectively; c) change the size of the sub-band of
at least one of the first or second frequency sub-bands; and d) change
the number of carriers included in at least one of the first and second
carriers.

23.-25. (canceled)

26. A base station comprising: at least one antenna; transmit circuitry
coupled to the at least one antenna configured to transmit a signal;
receive circuitry coupled to the at least one antenna configured to
receive a signal; base station circuitry configured to: for a
communication link between the base station and at least one relay
station with which the at least one relay station is communicating,
allocate a first frequency sub-band; for a communication link between the
base station and a first subset of one or more mobile stations with which
the base station is communicating, allocate a second frequency sub-band;
for a communication link between the at least one relay station and a
second subset of one or more mobile stations with which the at least one
relay station is communicating, allocate a third frequency sub-band; the
base station configure to notify the relay station regarding the location
of the allocated first, second and third sub-bands; wherein the first,
second and third frequency sub-bands are aggregate non-overlapping
sub-bands that collectively provide increased bandwidth.

27. The base station of claim 26, wherein one or more of the first,
second and third frequency sub-band include first, second and third
carrier frequencies, respectively.

28. The base station of claim 27 wherein one or more of the first, second
and third carrier frequencies are non-contiguous carrier frequencies
within the aggregate increased bandwidth.

29. The base station of claim 26 wherein the first, second and third
frequency sub-bands are contiguous sub-bands within the aggregate
increased bandwidth.

30. The base station of claim 26, the base station further configured to:
allocate in a down link (DL) frequency band a first DL frequency sub-band
and in an up link (UL) frequency band a first UL frequency sub-band;
allocate in the DL frequency band a second DL frequency sub-band and in
the UL frequency band a second UL frequency sub-band; allocate in the DL
frequency band a third DL frequency sub-band and in the UL frequency band
a third UL frequency sub-band.

31. The base station of claim 26, the base station further configured to:
in a first time slot for down link (DL) communications, allocate in a
frequency band the first frequency sub-band, the second frequency
sub-band and the third frequency sub-band; in a second time slot for up
link (UL) communications, allocate in the frequency band the first
frequency sub-band, the second frequency sub-band and the third frequency
sub-band.

32. The base station of claim 26, the base station further configured to:
a) i) allocate the first frequency sub-band as a dedicated sub-band; and
ii) allocate the third frequency sub-band as a dedicated sub-band; b)
dynamically assign at least one of the first and third sub-bands to a
different sub-band than the dedicated first or third sub-band,
respectively; c) change the size of the sub-band of at least one of the
first, second and third sub-bands; and d) change the number of carriers
included in at least one of the first, second and third carriers.

33.-35. (canceled)

36. A communication system comprising: at least one base station; at
least one relay station in communication with the at least one base
station; a first set of one or more mobile stations in communication with
the at least one base station; a second set of one or more mobile
stations in communication with the at least one relay station; for a
communication link between a base station of the at least one base
station and the at least one relay station with which the base station is
communicating, allocating a first frequency sub-band; for a communication
link between the base station and the first set of one or more mobile
stations with which the base station is communicating, allocating a
second frequency sub-band; for a communication link between the at least
one relay station and the second set of one or more mobile stations with
which the at least one relay station is communicating, allocating a third
frequency sub-band; the at least one relay station performing at least
one of: receiving signals on the first frequency sub-band and
transmitting signals on the third frequency sub-band simultaneously; and
transmitting signals on the first frequency sub-band and receiving
signals on the third frequency sub-band simultaneously; wherein the
first, second and third frequency sub-bands are aggregate non-overlapping
sub-bands that collectively provide increased bandwidth.

37.-50. (canceled)

Description:

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent
Application No. 61/060,995 filed on Jun. 12, 2008, which is hereby
incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] The invention relates to relays in wireless communication networks.

BACKGROUND OF THE INVENTION

[0003] A relay station acts as an intermediary between a base station and
a mobile station by communicating with the base station and mobile
station. In addition, the relay station may act as an intermediary
between a base station and a second relay station by communicating with
the base station and the second relay station or between a second relay
station and a mobile station by communicating with the second relay
station and the mobile station. To avoid self interference between a
transmitter and receiver in the relay station, usually the relay station
can not receive data and transmit data simultaneously in the same system
operation band. Different time slots are allocated to the links from base
station to relay station, from mobile station to relay station, or from
relay station to relay station for both frequency division duplexing
(FDD) and time division duplexing (TDD).

[0004] Some shortcomings of such a half-duplex FDD or TDD base relay
transmission are:

[0005] 1. a reduced efficiency of the system;

[0006] 2. modification of frame structure in necessary to accommodate the
half duplex nature of the transmissions;

[0007] 3. difficulty in supporting synchronous HARQ; and

[0008] 4. difficulty in monitoring all mobile stations.

SUMMARY OF THE INVENTION

[0009] In accordance with a first aspect of the invention there is
provided a method comprising: for a communication link between a base
station and at least one relay station with which the base station is
communicating, allocating a first frequency sub-band; for a communication
link between the base station and a first subset of one or more mobile
stations with which the base station is communicating, allocating a
second frequency sub-band; for a communication link between the at least
one relay station and a second subset of one or more mobile stations with
which the at least one relay station is communicating, allocating a third
frequency sub-band; the at least one relay station performing at least
one of: receiving signals on the first frequency sub-band and
transmitting signals on the third frequency sub-band simultaneously; and
transmitting signals on the first frequency sub-band and receiving
signals on the third frequency sub-band simultaneously; wherein the
first, second and third frequency sub-bands are aggregate non-overlapping
sub-bands that collectively provide increased bandwidth.

[0010] In some embodiments, one or more of the first, second and third
frequency sub-band include first, second and third carrier frequencies,
respectively.

[0011] In some embodiments, one or more of the first, second and third
carrier frequencies are non-contiguous carrier frequencies within the
aggregate increased bandwidth.

[0012] In some embodiments, the first, second and third frequency
sub-bands are contiguous sub-bands within the aggregate increased
bandwidth.

[0013] In some embodiments, allocating the first frequency sub-band
comprises allocating in a down link (DL) frequency band a first DL
frequency sub-band and in an up link (UL) frequency band a first UL
frequency sub-band; allocating the second frequency sub-band comprises
allocating in the DL frequency band a second DL frequency sub-band and in
the UL frequency band a second UL frequency sub-band; allocating the
third frequency sub-band comprises allocating in the DL frequency band a
third DL frequency sub-band and in the UL frequency band a third UL
frequency sub-band; the at least one relay station performing one or more
of receiving signals on the first DL frequency sub-band, transmitting
signals on the third DL frequency sub-band, transmitting signals on the
first UL frequency sub-band and receiving signals on the third UL
frequency sub-band simultaneously in a same time slot.

[0014] In some embodiments, in a first time slot for down link (DL)
communications, allocating in a frequency band the first frequency
sub-band, the second frequency sub-band and the third frequency sub-band;
in a second time slot for up link (UL) communications, allocating in the
frequency band the first frequency sub-band, the second frequency
sub-band and the third frequency sub-band; the at least one relay station
performing: receiving signals on the first frequency sub-band and
transmitting signals on the third frequency sub-band simultaneously
during a first time slot; and transmitting signals on the first frequency
sub-band and receiving signals on the third frequency sub-band
simultaneously in a same time slot.

[0015] In some embodiments the method further comprises at least one of:
allocating the first frequency sub-band comprises allocating a dedicated
sub-band; and allocating the third frequency sub-band comprises
allocating a dedicated sub-band.

[0016] In some embodiments the method further comprises: dynamically
assigning at least one of the first and third sub-band to a different
sub-band than the dedicated first or third frequency sub-band,
respectively.

[0017] In some embodiments the method further comprises: changing the size
of the sub-band of at least one of the first, second and third frequency
sub-bands.

[0018] In some embodiments, the method further comprises: changing the
number of carriers included in at least one of the first, second and
third carriers.

[0019] In some embodiments, the first, second and third frequency
sub-bands are each greater than 10 MHz and less than 30 MHz.

[0020] In some embodiments, the relay station is an LTE enabled relay
station.

[0021] In some embodiments, the LTE enabled relay station configured to
support legacy mobile stations.

[0022] In some embodiments, the method further comprises: applying
transmission power distribution control to reduce the interference
between transmissions and receptions of the relay station.

[0023] in some embodiments, applying transmission power distribution
control comprises: transmitting signals on the first or third frequency
sub-bands using a narrow band signal with a higher power than a wide band
signal having a lower power, to reduce to the size of a guard band
between transmissions and receptions of the relay station.

[0024] In accordance with a second aspect of the invention, there is
provided a relay station comprising; at least one antenna; transmit
circuitry coupled to the at least one antenna configured to transmit a
signal; receive circuitry coupled to the at least one antenna configured
to receive a signal; relay circuitry configured to: for a communication
link between a base station with which the relay station is communicating
and the relay station, allocate a first frequency sub-band; for a
communication link between the relay station and a set of one or more
mobile stations with which the relay station is communicating, allocate a
second frequency sub-band; the relay station configured to perform at
least one of: receive signals on the first frequency sub-band and
transmit signals on the second frequency sub-band simultaneously; and
transmit signals on the first frequency sub-band and receive signals on
the second frequency sub-band simultaneously; wherein the first and
second frequency sub-bands are aggregate non-overlapping sub-bands that
collectively provide increased bandwidth in conjunction with a third
frequency sub-band for a communication link between the base station and
a second set of one or more mobile stations with which the base station
is communicating.

[0025] In some embodiments, one or more of the first, second and third
frequency sub-band include first, second and third carrier frequencies,
respectively.

[0026] In some embodiments, one or more of the first, second and third
carrier frequencies are non-contiguous carrier frequencies within the
aggregate increased bandwidth.

[0027] In some embodiments, the first, second and third frequency
sub-bands are contiguous sub-bands within the aggregate increased
bandwidth.

[0028] In some embodiments, the relay station is further configured to
allocate in a down link (DL) frequency band a first DL frequency sub-hand
and in an up link (UL) frequency band a first UL frequency sub-band;
allocate in the DL frequency band a second DL frequency sub-band and in
the UL frequency band a second UL frequency sub-band; the relay station
configured to perform one or more of: receive signals on the first DL
frequency sub-band, transmit signals on the second DL frequency sub-band,
transmit signals on the first UL frequency sub-band and receive signals
on the second UL frequency sub-band simultaneously in a same time slot.

[0029] In some embodiments, the relay station is further configured to: in
a first time slot for down link (DL) communications, allocate in a
frequency band the first frequency sub-band and the second frequency
sub-band; in a second time slot for up link (UL) communications, allocate
in the frequency band the first frequency sub-band and the second
frequency sub-band; the relay station configured to perform: receive
signals on the first frequency sub-band and transmit signals on the
second frequency sub-band simultaneously during the first time slot; and
transmit signals on the first frequency sub-band and receive signals on
the second frequency sub-band simultaneously in the second time slot.

[0030] In some embodiments, the relay station is further configured to:
allocate the first frequency sub-band as a dedicated sub-band; and
allocate the second frequency sub-band as a dedicated sub-band.

[0031] In some embodiments, the relay station is further configured to:
dynamically assign at least one of the first and second frequency
sub-bands to a different sub-band than the dedicated first or second
frequency sub-band, respectively.

[0032] In some embodiments, the relay station is further configured to:
change the size of the sub-band of at least one of the first or second
frequency sub-bands.

[0033] In some embodiments, the relay station is further configured to:
change the number of carriers included in at least one of the first and
second carriers.

[0034] In accordance with a third aspect of the invention, there is
provided a base station comprising: at least one antenna; transmit
circuitry coupled to the at least one antenna configured to transmit a
signal; receive circuitry coupled to the at least one antenna configured
to receive a signal; base station circuitry configured to: for a
communication link between the base station and at least one relay
station with which the at least one relay station is communicating,
allocate a first frequency sub-band; for a communication link between the
base station and a first subset of one or more mobile stations with which
the base station is communicating, allocate a second frequency sub-band;
for a communication link between the at least one relay station and a
second subset of one or more mobile stations with which the at least one
relay station is communicating, allocate a third frequency sub-band; the
base station configure to notify the relay station regarding the location
of the allocated first, second and third sub-bands; wherein the first,
second and third frequency sub-bands are aggregate non-overlapping
sub-bands that collectively provide increased bandwidth.

[0035] In some embodiments, one or more of the first, second and third
frequency sub-band include first, second and third carrier frequencies,
respectively.

[0036] In some embodiments, one or more of the first, second and third
carrier frequencies are non-contiguous carrier frequencies within the
aggregate increased bandwidth.

[0037] In some embodiments, the first, second and third frequency
sub-bands are contiguous sub-bands within the aggregate increased
bandwidth.

[0038] In some embodiments, the base station is further configured to:
allocate in a down link (DL) frequency band a first DL frequency sub-band
and in an up link (UL) frequency band a first UL frequency sub-band;
allocate in the DL frequency band a second DL frequency sub-band and in
the UL frequency band a second UL frequency sub-band; allocate in the DL
frequency band a third DL frequency sub-band and in the UL frequency band
a third UL frequency sub-band.

[0039] In some embodiments, the base station is further configured to: in
a first time slot for down link (DL) communications, allocate in a
frequency band the first frequency sub-band, the second frequency
sub-band and the third frequency sub-band; in a second time slot for up
link (UL) communications, allocate in the frequency band the first
frequency sub-band, the second frequency sub-band and the third frequency
sub-band.

[0040] In some embodiments, the base station is further configured to:
allocate the first frequency sub-band as a dedicated sub-band; and
allocate the third frequency sub-band as a dedicated sub-band.

[0041] In some embodiments, the base station is further configured to:
dynamically assign at least one of the first and third sub-bands to a
different sub-band than the dedicated first or third sub-band,
respectively.

[0042] In some embodiments, the base station is further configured to:
change the size of the sub-band of at least one of the first, second and
third sub-bands.

[0043] In some embodiments, the base station is further configured to:
change the number of carriers included in at least one of the first,
second and third carriers.

[0044] In accordance with a fourth aspect of the invention, there is
provided a communication system comprising: at least one base station; at
least one relay station in communication with the at least one base
station; a first set of one or more mobile stations in communication with
the at least one base station; a second set of one or more mobile
stations in communication with the at least one relay station; for a
communication link between a base station of the at least one base
station and the at least one relay station with which the base station is
communicating, allocating a first frequency sub-band; for a communication
link between the base station and the first set of one or more mobile
stations with which the base station is communicating, allocating a
second frequency sub-band; for a communication link between the at least
one relay station and the second set of one or more mobile stations with
which the at least one relay station is communicating, allocating a third
frequency sub-band; the at least one relay station performing at least
one of: receiving signals on the first frequency sub-band and
transmitting signals on the third frequency sub-band simultaneously; and
transmitting signals on the first frequency sub-band and receiving
signals on the third frequency sub-band simultaneously; wherein the
first, second and third frequency sub-bands are aggregate non-overlapping
sub-bands that collectively provide increased bandwidth.

[0045] In some embodiments, one or more of the first, second and third
frequency sub-band include first, second and third carrier frequencies,
respectively.

[0046] In some embodiments, one or more of the first, second and third
carrier frequencies are non-contiguous carrier frequencies within the
aggregate increased bandwidth.

[0047] In some embodiments, the first, second and third frequency
sub-bands are contiguous sub-bands within the aggregate increased
bandwidth.

[0048] In some embodiments, allocating the first frequency sub-band
comprises allocating in a down link (DL) frequency band a first DL
frequency sub-band and in an up link (UL) frequency band a first UL
frequency sub-band; allocating the second frequency sub-band comprises
allocating in the DL frequency band a second DL frequency sub-band and in
the UL frequency band a second UL frequency sub-band; allocating the
third frequency sub-band comprises allocating in the DL frequency band a
third DL frequency sub-band and in the UL frequency band a third UL
frequency sub-band; the at least one relay station performing one or more
of receiving signals on the first DL frequency sub-band, transmitting
signals on the third DL frequency sub-band, transmitting signals on the
first UL frequency sub-band and receiving signals on the third UL
frequency sub-band simultaneously in a same time slot.

[0049] In some embodiments, in a first time slot for down link (DL)
communications, allocating in a frequency band the first frequency
sub-band, the second frequency sub-band and the third frequency sub-band;
in a second time slot for up link (UL) communications, allocating in the
frequency band the first frequency sub-band, the second frequency
sub-band and the third frequency sub-band; the at least one relay station
performing: receiving signals on the first frequency sub-band and
transmitting signals on the third frequency sub-band simultaneously
during the first time slot, transmitting signals on the first frequency
sub-band and receiving signals on the third frequency sub-band
simultaneously in the second time slot.

[0050] In some embodiments, the system further comprises at least one of:
allocating the first frequency sub-band comprises allocating a dedicated
sub-band; and allocating the third frequency sub-band comprises
allocating a dedicated sub-band.

[0051] In some embodiments, the system further comprises dynamically
assigning at least one of the first and third sub-band to a different
sub-band than the dedicated first or third frequency sub-band,
respectively.

[0052] In some embodiments, the system further comprises changing the size
of the sub-band of at least one of the first, second and third frequency
sub-bands.

[0053] In some embodiments, the system further comprises changing the
number of carriers included in at least one of the first, second and
third carriers.

[0054] In some embodiments, the first, second and third frequency
sub-bands are each greater than 10 MHz and less than 30 MHz.

[0055] In some embodiments, the relay station is an LTE enabled relay
station.

[0056] In some embodiments, the LTE enabled relay station is configured to
support legacy mobile stations.

[0057] In some embodiments, the system further comprises applying
transmission power distribution control to reduce the interference
between transmissions and receptions of the relay station.

[0058] In some embodiments, applying transmission power distribution
control comprises: transmitting signals on the first or third sub-bands
using a narrow band signal with a higher power than a wide band signal
having a lower power, to reduce to the size of a guard band between
transmissions and receptions of the relay station.

[0059] Other aspects and features of the present invention will become
apparent to those ordinarily skilled in the art upon review of the
following description of specific embodiments of the invention in
conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Embodiments of the invention will now be described with reference
to the attached drawings in which:

[0061] FIG. 1 is a block diagram of a cellular communication system;

[0062]FIG. 2 is a schematic diagram representing different layers
utilized in network communications for an example of a non-contiguous
spectrum aggregation according to an embodiment of the invention;

[0063] FIGS. 3a, 3b and 3c are block diagrams of examples of DL FDD
in-band communications and UL FDD in-band communications between a base
station and a mobile station via a relay station according to an
embodiment of the invention;

[0064] FIGS. 4a, 4b and 4c are block diagrams of examples of DL TDD
in-band communications and UL FDD in-band communications between a base
station and a mobile station via a relay station according to an
embodiment of the invention;

[0065]FIG. 5 is a schematic diagram representing different layers
utilized in network communications for an example of a contiguous
spectrum aggregation according to an embodiment of the invention;

[0066] FIGS. 6a, 6b and 6c are block diagrams of examples of DL FDD
in-band communications and UL FDD in-band communications between a base
station and a mobile station via a relay station according to an
embodiment of the invention;

[0067] FIGS. 7a, 7b and 7c are block diagrams of examples of DL TDD
in-band communications and UL FDD in-band communications between a base
station and a mobile station via a relay station according to an
embodiment of the invention;

[0068] FIG. 8 is a flow chart representing an example of a method
according to an embodiment of the invention;

[0069]FIG. 9 is an example of an aggregated spectrum illustrating
transmission power distribution control according to an aspect of the
invention;

[0070]FIG. 10 is a block diagram of an example base station that might be
used to implement some embodiments of the present 5 application;

[0071]FIG. 11 is a block diagram of an example wireless terminal that
might be used to implement some embodiments of the present application;

[0072]FIG. 12 is a block diagram of an example relay station that might
be used to implement some embodiments of the present application;

[0073] FIG. 13 is a block diagram of a logical breakdown of an example
OFDM transmitter architecture that might be used to implement some
embodiments of the present application; and

[0074]FIG. 14 is a block diagram of a logical breakdown of an example
OFDM receiver architecture that might be used to implement some
embodiments of the present application;

[0075]FIG. 15A is a block diagram of an SC-FDMA transmitter used to
implement some embodiments of the present application; and

[0076] FIG. 15b is a block diagram of an SC-FDMA receiver used to
implement some embodiments of the present application.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

[0077] Referring to the drawings, FIG. 1 shows a base station controller
(BSC) 10 which controls wireless communications within multiple cells 12,
which cells are served by corresponding base stations (BS) 14. In some
configurations, each cell is further divided into multiple sectors 13 or
zones (not shown). In general, each base station 14 facilitates
communications using OFDM with mobile and/or wireless terminals 16, which
are within the cell 12 associated with the corresponding base station 14.
The movement of the mobile terminals 16 in relation to the base stations
14 results in significant fluctuation in channel conditions. As
illustrated, the base stations 14 and mobile terminals 16 may include
multiple antennas to provide spatial diversity for communications. In
some configurations, relay stations 15 may assist in communications
between base stations 14 and wireless terminals 16. Wireless terminals 16
can be handed off 18 from any cell 12, sector 13, zone (not shown), base
station 14 or relay 15 to an other cell 12, sector 13, zone (not shown),
base station 14 or relay 15. In some configurations, base stations 14
communicate with each and with another network (such as a core network or
the internet, both not shown) over a backhaul network 11. In some
configurations, a base station controller 10 is not needed.

[0078] International Mobile Telecommunications (IMT) Advanced technology,
also known as 4th Generation (4G) targets to support up to 100 MHz
BW. LTE currently supports single carrier bandwidths of up to 20 MHz. The
present application describes a multi-carrier approach in which some
embodiments of the invention provide a simple solution of aggregating
multiple single carrier bandwidths to obtain a wider bandwidth (>20
MHz). Such an approach may extend Long Term Evolution (LTE) bandwidth to
greater than that provided by a single carrier, yet maintain full
backward compatibility with technologies that predate 4G technology and
utilize smaller, single carrier bandwidths.

[0079] A relay station that can both transmit and receive simultaneously
may be included in the spectrum aggregated communication system to
optimize system performance possibly by using one or more of the
following approaches;

[0080] 1. maintaining non-interrupted bi-directional communications links
between a base station and at least one relay station as well as between
a relay station and at least one mobile station;

[0081] 2. using a dedicated carrier based relay station for non-contiguous
spectrum aggregation for time divisional duplexing (TDD) and/or frequency
division duplexing (FDD);

[0082] 3. using a dedicated sub-band based relay station for contiguous
spectrum aggregation for TDD and/or FDD;

[0083] 4. using flexible channel resource allocations for at least one
relay station and at least one mobile station;

[0085] 6. using transmission power distribution control to reduce
interference between simultaneous transmitting and receiving in at least
one relay station; and

[0086] 7. controlling the separation of the available guard band between
carriers and/or sub-bands used for simultaneous transmitting and
receiving.

[0087] A relay station may be used to improve cell coverage and throughput
for LTE. As communication between the relay station and mobile stations
occur in the aggregated bandwidth that also includes bandwidth for
communications between the base station and mobile stations, the relay
station communications are considered in-band communications.

[0088] Some embodiments of the invention provide schemes to more
efficiently introduce the use of relay stations into broad band LTE-A
communication systems.

[0089] While embodiments of the invention have been described above with
regard to LTE-A, it is to be understood that embodiments of the invention
may be applicable to other types of communication standards.

[0090] Spectrum aggregation can be realized by aggregating contiguous
and/or non-contiguous spectrum in different bands. Some embodiments of
the invention may be implemented by aggregating non-contiguous single
carrier bands. In such embodiments, separate and non-overlapping carriers
are allocated for communication between the base station and mobile
stations that the base station communicates with directly which are a
single hop from the base station, for communication between the base
station and at least one relay station that the base station communicates
with directly which is a single hop from the base station, and for
communication between the at least one relay station and mobile stations
that the at least one relay station communicates with directly which are
at least two hops away from the base station. One or more carriers may be
used for base station to mobile station communications, base station to
relay station communications, relay station to relay station
communications, and relay station to mobile station communications. In
addition, carriers may be allocated for communication between a relay one
hop away from the base station and a relay two hops away from the base
station and for communication between with the relay two hops away from
the base station and one or more mobile stations that the two hop away
relay may communicate with. In some embodiments, not all of the carriers
within the aggregate spectrum band are used for communication. Any
unutilized carriers result in gaps between the carriers that are used.
Such an arrangement is therefore considered "non-contiguous", as not all
of the carriers are utilized.

[0091] Some embodiments of the invention may be implemented by aggregating
contiguous sub-bands. The sub-bands are allocated for communication
between the base station and mobile stations that the base station
communicates with directly which are a single hop from the base station,
for communication between the base station and at least one relay station
that the base station communicates with directly which is a single hop
from the base station, and for communication between the at least one
relay station and mobile stations that the at least one relay station
communicates with directly which are at least two hops away from the base
station. In addition, sub-bands may be allocated for communication
between a relay one hop away from the base station and a relay two hops
away from the base station and for communication between with the relay
two hops away from the base station and one or more mobile stations that
the two hop away relay may communicate with. When all of the sub-bands in
the aggregated spectrum are used in the manner described above, the
result is that the sub-bands are arranged in a "contiguous" manner.

Relay Station for Non-Contiguous Spectrum Aggregation

[0092] In some embodiments, in a non-contiguous spectrum aggregation
scenario, a relay station is supported by reserving a dedicated carrier
(Carrier R-B) for communications between the relay station and the base
station. In some embodiments, in a non-contiguous spectrum aggregation
scenario, a relay station is supported by dynamically scheduling a
carrier (Carrier R-B) for data exchange between the base station and the
relay station.

[0093] To reduce in-band transmit/receive interference at the relay
station, carriers (Carrier R-B) used for communication between the base
station and one hop away relay stations should be spaced apart from
neighbour carriers. In some embodiments, guard bands are in place between
the carriers. Neighbour carriers may include carriers (Carrier B) used
for communication between the base station and one hop away mobile
stations (Carrier B). Neighbour carriers may also include carriers
(Carrier R-UE) used for communication between the relay station and one
or more mobile stations with which the relay station may be
communicating. The farther apart that Carrier R-B and Carrier R-UE are
spaced, the greater amount of reduction of in-band transmit/receive
interference should occur. In some embodiments, there are alternative
ways to reduce interference rather than a large guard band, such as
transmission power distribution control, which will be discussed below.

[0094]FIG. 2 illustrates a schematic diagram representing different
layers utilized in network communications. In the physical layer (PHY),
which includes the basic hardware transmission technologies used in the
network, the respective carriers, Carrier R-UE 210, Carrier B 212,214 and
Carrier R-B 216, are illustrated as separate, non-overlapping carriers.
The media access layer (MAC) 220, which is a sub-layer of the data link
layer and provides addressing and channel access control mechanisms that
make it possible for network nodes to communicate within the network, is
illustrated as common to all the PHY layer carriers in the aggregated
spectrum. That is the MAC layer is adapted to have access to all the
separate carriers and by collectively utilizing the carriers, provide an
increased bandwidth. The common MAC layer is illustrated as being in
communication with upper layers 230 in the network hierarchy.

[0095] In some embodiments, the base station communicating with the one or
more relay station allocates the carrier locations in the aggregated
spectrum to be used for Carrier R-B, Carrier R-UE and Carrier B. In some
embodiments a relay station may provide the base station with information
to aid in identifying carrier locations and/or a number of carriers that
are needed with respect to at least one of Carrier R-B and Carrier R-UE.

[0096] In some embodiments, more than one carrier can be assigned as
Carrier R-B. The number of Carrier R-B's may be adjusted according to the
bandwidth requirement for communications between the base station and the
at least one relay station.

[0097] In some embodiments, more than one carrier can be assigned as
Carrier R-UE. The number of Carrier R-UE's may be adjusted according to
the bandwidth requirement for communications between a relay station and
at least one mobile station with which the relay station is
communicating.

[0098] In some embodiments, more than one carrier can be assigned as
Carrier B. The number of Carrier B's may be adjusted according to the
bandwidth requirement for communications between the base station and at
least one mobile station one hop away from the base station with which
the base station is communicating.

[0099] In some embodiments, for supporting legacy mobile stations, in
particular, but not limited to the case in which legacy mobile stations
are allocated specific carriers in the aggregate spectrum that may not
align with a desired carrier location in an LTE-A enabled network, the
locations of Carrier R-B and Carrier R-UE may change from time to time to
accommodate the legacy mobile stations and/or the relay stations that are
in communication with the legacy mobile stations.

[0100] In some embodiments, the change of carrier locations to support
legacy users (carrier hopping) of relay links occurs on a time slot by
time slot basis. In some embodiments, one or more consecutive time slots
have a first carrier location arrangement in the aggregate spectrum and a
subsequent one or more consecutive time slots have a second carrier
location arrangement in the aggregate spectrum to support the legacy
mobile stations, which is different than the first carrier location
arrangement. This arrangement of time slots having different carrier
location arrangements may be repeated over time. In some embodiments, the
second carrier location arrangement of subsequent repetitions of the
second carrier location arrangement may change over time. In some
embodiments, the number of time slots of either the first or second
carrier location arrangements can vary in number. In some embodiments,
more than two groups of one or more time slots may be used, each group of
one or more time slots having a different carrier location arrangement.

[0101] In some embodiments, one or more carrier locations of the aggregate
spectrum use time division duplexing to separate relay station reception
and transmission in the time domain to support legacy mobile stations,
while other carrier locations maintain a non-interrupted transmission and
reception of communications between the relay station and the base
station and/or between the relay station and one or more mobile station.
In a particular example, referring to FIG. 2, in a first time slot a
relay station receives communication on Carrier R-B 216 from a base
station, but does not transmit on carrier R-B 216 to the base station,
and in second time slot the relay station transmits communication on
Carrier R-B 216 to the base station, but does not receive on carrier R-B
216 from the base station.

FDD In-band Relay

[0102] One manner of maintaining non-interrupted bi-directional links
between a base station and a relay station as well as bi-directional
links between the relay station and one or more mobile station is a FDD
in-band implementation.

[0103] Referring to FIGS. 3a and 3b, an FDD in-band implementation for
non-contiguous aggregation spectrum will now be described.

[0104] FIG. 3a illustrates a block diagram representation of a base
station (eNB) 302 communicating via a relay station (RN) 304 with a
mobile station (UE) 306 in a down link (DL) direction from the base
station 302 to the mobile station 306 using an aggregate spectrum. For a
particular time slot T1, on a DL frequency band F1, the relay station 304
can simultaneously receive data from the base station 302 on Carrier
R-BDL, and transmit data to the mobile station 306 on Carrier
R-UEDL. Data transmitted from the base station 302 to mobile
stations one hop away (not shown) from the base station 302 are
transmitted on Carrier BDL within the in-band spectrum. As these
signals do not dissipate at a distance equal to the relay station 304,
they are illustrated continuing onto the mobile station 306. This does
not necessarily mean that Carrier BDL will reach the mobile station
that the relay station is communicating with. Carrier BDL is
illustrated to indicate potential interference with Carrier R-BDL
and Carrier R-UEDL.

[0105] In some embodiments, the locations of the different carriers are
maintained in the same positions for each time slot. In some embodiments,
the locations of the different carriers are in different positions in
different time slots, as described above. Such embodiments may be useful
in supporting legacy mobile stations.

[0106]FIG. 3B illustrates a block diagram representation of the base
station 302 communicating via the relay station 304 with the mobile
station 306 in an up link (UL) direction from the mobile station 306 to
the base station 302. For the time slot T1, on a UL frequency band F2,
the relay station 304 can simultaneously receive data from the mobile
station 306 on Carrier R-UEUL and transmit data to the base station
302 on Carrier R-BUL. Data transmitted from the mobile stations one
hop away (not shown) from the base station 302 to the base station 302
are transmitted on Carrier BUL within the in-band spectrum. These
signals may typically originate close to the base station or close to the
relay station, but they are illustrated between the mobile station 306
and the base station 302. Carrier BUL is illustrated to indicate
potential interference with Carrier R-BUL and Carrier R-UEUL.

[0107] In some embodiments, the locations of the different carriers are
maintained in the same positions for each time slot. In some embodiments,
the locations of the different carriers are in different positions in
different time slots, as described above.

[0109] In some embodiments, any of Carrier R-BDL, Carrier
R-UEDL, Carrier R-BUL, and Carrier R-UEUL can be re-used
by the base station and relay station to further improve the spectrum
efficiency. For example, in a base station transmitting over multiple
sectors, Carrier R-BDL (or R-BUL) may be reused in sectors that
are well separated such that little to no interference would occur.
Similarly, for a given base station, in sectors that are not in close
proximity, Carrier R-UEDL (or R-UEUL) may be re-used between
relay stations and mobile stations.

TDD In-band Relay

[0110] Another manner of maintaining non-interrupted bi-directional links
between a base station and a relay station as well as bi-directional
links between the relay station and one or more mobile station during DL
and UL sub-frames is a TDD in-band implementation.

[0111] Referring to FIGS. 4a and 4b, a TDD in-band implementation for
non-contiguous aggregation spectrum will now be described.

[0112]FIG. 4A illustrates a block diagram representation of a base
station (eNB) 402 communicating via a relay station (RN) 404 with a
mobile station (UE) 406 in a down link direction from the base station
402 to the mobile station 406. For a DL time slot T1, on a frequency band
F1, the relay station 404 can simultaneously receive data from the base
station 402 on Carrier R-B and transmit data to the mobile station 406 on
Carrier R-UE. Data transmitted from the base station 402 to mobile
stations one hop away (not shown) from the base station 402 are
transmitted on Carrier B within the in-band spectrum. As these signals do
not dissipate at a distance equal to the relay station 404, they are
illustrated continuing onto the mobile station 406. This does not
necessarily mean that Carrier B will reach the mobile station that the
relay station is communicating with. Carrier B is illustrated to indicate
potential interference with Carrier R-B and Carrier R-UE.

[0113] In some embodiments, the locations of different carriers are
maintained in the same positions for each time slot. In some embodiments,
the locations of different carriers are in different positions, as
described above.

[0114]FIG. 4B illustrates a block diagram representation of the base
station 402 communicating via the relay station 404 with the mobile
station 406 in an up link direction from the mobile station 406 to the
base station 402. For a UL time slot T2, on the frequency band F1, the
relay station 404 can simultaneously receive data from the mobile station
406 on Carrier R-UE and transmit data to the base station 402 on Carrier
R-B. Data transmitted from the mobile stations one hop away (not shown)
from the base station 402 to the base station 402 are transmitted on
Carrier B within the in-band spectrum. These signals may typically
originate close to the base station or close to the relay station, but
they are illustrated between the mobile station 406 and the base station
402. Carrier B is illustrated to indicate potential interference with
Carrier R-B and Carrier R-UE.

[0115] In some embodiments, the locations of different carriers being are
maintained in the same positions for each time slot. In some embodiments,
the locations of different carriers are in different positions, as
described above.

[0116] While a single base station, single relay station and single mobile
station are illustrated in FIGS. 3a, 3b, 4a and 4b, it is to be
understood that a network may have multiple base stations, each base
station communicating with one or more relay stations and possibly one or
more one hop away mobile stations, each relay station communicating with
one or more mobile station and possibly one or more second relay stations
that may communicate with mobile stations.

[0117] In some embodiments, Carrier R-B and Carrier R-UE can be re-used by
the base station and relay station to further improve the spectrum
efficiency.

[0118] FIG. 4c illustrates an example aggregate spectrum for each of two
time slots as described above with regard to FIGS. 4a and 4b. FIG. 4c
illustrates a first time slot T1 in which DL communications occur on
frequency band F1, which includes Carrier R-B, Carrier R-UE and Carrier B
and a second time slot T2 in which UL communications occur on frequency
band F1, which includes Carrier R-E, Carrier R-UE and Carrier B.

Relay for Contiguous Spectrum Aggregation

[0119] In some embodiments, in a contiguous spectrum aggregation scenario,
a relay station can be supported by reserving a dedicated sub-band
(Sub-band R-B) for communications between the relay station and the base
station. In some embodiments, in a contiguous spectrum aggregation
scenario, a relay station can be supported by dynamically scheduling a
sub-baud (Sub-band R-B) for data exchange between the base station and
the relay station.

[0120] To reduce in-band transmit/receive interference at the relay
station, a sub-band (Sub-band R-B) used for communication between the
base station and one hop away relay stations should be spaced apart from
a sub-band (Sub-band R-UE) used for communication between the relay
station and one or more mobile stations with which the relay station may
be communicating. The farther apart that Sub-band R-B and Sub-band R-UE
are spaced, the greater amount of reduction of in-band transmit/receive
interference should occur. In some embodiments, there are alternative
ways to reduce interference rather than a large guard band, such as
transmission power distribution control, which will be discussed below.

[0121]FIG. 5 illustrates a schematic diagram representing different
layers utilized in network communications. FIG. 5 is similar in some
respects to FIG. 2. The main difference being that FIG. 2 illustrates
non-contiguous carriers in the aggregated spectrum, while FIG. 5
illustrates a contiguous group of sub-bands in the aggregated spectrum.
In the physical layer (PHY), the respective sub-bands, Sub-band R-UE 510,
Sub-band B 512,514,516 and Sub-band R-B 518, are illustrated as separate
respective sub-bands, which collectively occupy the entire spectrum. The
MAC layer 520 is illustrated as common to all the PHY layer sub-bands.
The common MAC layer is illustrated as being in communication with upper
layers 530 of the network.

[0122] In some embodiments, the size of Sub-band R-B may be adjusted
according to the bandwidth requirement for communications between the
base station and the at least one relay station.

[0123] In some embodiments, the size of Sub-band R-UE may be adjusted
according to the bandwidth requirement for communications between a relay
station and at least one mobile station with which the relay station is
communicating.

[0124] In some embodiments, the size of Sub-band B may be adjusted
according to the bandwidth requirement for communications between the
base station and at least one mobile station one hop away from the base
station with which the base station is communicating.

[0125] In some embodiments, for supporting legacy mobile stations, in
particular, but not limited to the case in which legacy mobile stations
are allocated specific carriers that may not align with desired sub-bands
in an LTE-A enabled network, the locations of Sub-band R-B and Sub-band
R-UE may change from time to time.

[0126] In some embodiments, the change of sub-band locations to support
legacy users (sub-band hopping) of relay links may occur such that the
change may occur on a time slot by time slot basis. In some embodiments,
several consecutive time slots have a first sub-band location arrangement
and a subsequent one or more consecutive time slots have a second
sub-band location arrangement, which is different than the first sub-band
location arrangement, to support the legacy mobile stations. This
arrangement of time slots may be repeated for the first and second
sub-band location arrangements. In some embodiments, the second sub-band
location arrangement of subsequent repetitions of the second sub-band
location arrangement may change over time. In some embodiments, the
number of time slots of either the first or second sub-band location
arrangements can vary in number.

[0127] In some embodiments, some sub-band locations of the bandwidth use
time division duplexing to separate relay station reception and
transmission in the time domain to support legacy mobile stations, while
other sub-band locations maintain a non-interrupted transmission and
reception of communications between the relay station and the base
station and/or between the relay station and one or more mobile station.
In a particular example, referring to the arrangement of FIG. 5, in a
first time slot a relay station receives communication on Sub-band R-B
518 from a base station, but does not transmit on Sub-band R-B 518 to the
base station, and in a second time slot the relay station transmits
communication on Sub-band R-B 518 to the base station, but does not
receive on Sub-band R-B 518 from the base station.

FED In-Band Relay

[0128] One manner of maintaining non-interrupted bi-directional links
between a base station and a relay station as well as bi-directional
links between the relay station and one or more mobile station is a FDD
in-band implementation.

[0129] Referring to FIGS. 6a and 6b, an FDD in-band implementation for
contiguous aggregation spectrum will now be described.

[0130] FIG. 6a illustrates a block diagram representation of a base
station (eNB) 602 communicating via a relay station (RN) 604 with a
mobile station (UE) 606 in a down link direction from the base station
602 to the mobile station 606. For a particular time slot T1, on a DL
frequency band F1, the relay station 604 can simultaneously receive data
from the base station 602 on Sub-band R-BDL and transmit data to the
mobile station 606 on Sub-band R-UEDL. Data transmitted from the
base station 602 to mobile stations one hop away (not shown) from the
base station 602 are transmitted on Sub-band BDL within the in-band
spectrum. As these signals do not dissipate at a distance equal to the
relay station 604, they are illustrated continuing onto the mobile
station 606. This does not necessarily mean that Carrier BDL will
reach the mobile station that the relay station is communicating with.
Carrier BDL is illustrated to indicate potential interference with
Carrier R-BDL and Carrier R-UEDL.

[0131] In some embodiments, the locations of different sub-bands are
maintained in the same positions for each time slot. In some embodiments,
the locations of different sub-bands are in different positions, in a
similar manner to the different carrier positioning described above for
the non-contiguous embodiments. Such embodiments may be useful in
supporting legacy mobile stations.

[0132]FIG. 6B illustrates a block diagram representation of the base
station 602 communicating via the relay station 604 with the mobile
station 606 in an up link direction from the mobile station 606 to the
base station 602. For the time slot T1, on a UL frequency band F2, the
relay station 604 can simultaneously receive data from the mobile station
606 on Sub-band R-UEUL and transmit data to the base station 602 on
Sub-band R-BUL. Data transmitted from the mobile stations one hop
away (not shown) from the base station 602 to the base station 602 are
transmitted on Sub-band BUL within the in-band spectrum. These
signals may typically originate close to the base station or close to the
relay station, but they are illustrated between the mobile station 606
and the base station 602. Carrier BUL is illustrated to indicate
potential interference with Carrier R-BUL and Carrier R-UEUL.

[0133] In some embodiments, the locations of different sub-bands are
maintained in the same positions for each time slot. In some embodiments,
the locations of sub-bands are in different positions.

[0134]FIG. 6c illustrates an example spectrum pertaining to FIGS. 6a and
6b. FIG. 6c illustrates for a given time slot T1 a DL frequency band F1,
including Sub-band R-UEDL, Sub-band BDL and Sub-band R-BDL
and an UL frequency band F2, including Sub-band R-UEUL, Sub-band
BUL and Sub-band R-BUL.

[0135] In some embodiments, any of Sub-band R-BDL, Sub-band
R-UEDL, Sub-band R-BUL and Sub-band R-UEUL can be re-used
by the base station and relay station to further improve the spectrum
efficiency. For example, in a base station transmitting over multiple
sectors, sub-band R-BDL (or R-BUL) may be reused in sectors
that are well separated such that little to no interference would occur.
Similarly, for a given base station, in sectors that are not in close
proximity, Sub-band R-UEDL (or R-UEUL) may be re-used between
relay stations and mobile stations.

TDD In-Band Relay

[0136] Another manner of maintaining non-interrupted bi-directional links
between a base station and a relay station as well as bi-directional
links between the relay station and one or more mobile station during DL
and UL sub-frames is a TDD in-band implementation.

[0137] Referring to FIGS. 7a and 7b, a TDD in-band implementation for
contiguous aggregation spectrum will now be described.

[0138] FIG. 7a illustrates a block diagram representation of a base
station (eNB) 702 communicating via a relay station (RN) 704 with a
mobile station (UE) 706 in a down link direction from the base station
702 to the mobile station 706. For a DL time slot T1, on a frequency band
F1, the relay station 704 can simultaneously receive data from the base
station 702 on Sub-band R-B and transmit data to the mobile station 706
on Sub-band R-UE. Data transmitted from the base station 702 to mobile
stations one hop away (not shown) from the base station 702 are
transmitted on Sub-band B within the in-band spectrum. These signals may
typically originate close to the base station or close to the relay
station, but they are illustrated between the mobile station 706 and the
base station 702. Carrier B is illustrated to indicate potential
interference with Carrier R-B and Carrier R-UE.

[0139] In some embodiments, such an implementation occurs with the
locations of sub-bands being maintained in the same positions for each
time slot. In some embodiments, such an implementation occurs with the
locations of sub-bands having different positions.

[0140] FIG. 7b illustrates a block diagram representation of the base
station 702 communicating via the relay station 704 with the mobile
station 706 in an up link direction from the mobile station 706 to the
base station 702. For a UL time slot T2, on the frequency band F1, the
relay station 704 can simultaneously receive data from the mobile station
706 on Sub-band R-UE and transmit data to the base station 702 on
Sub-band R-B. Data transmitted from the mobile stations one hop away (not
shown) from the base station 702 to the base station 702 are transmitted
on Sub-band B within the in-band spectrum. These signals may typically
originate close to the base station or close to the relay station, but
they are illustrated between the mobile station 706 and the base station
702. Carrier B is illustrated to indicate potential interference with
Carrier R-B and Carrier R-UE.

[0141] In some embodiments, the locations of different sub-bands are
maintained in the same positions for each time slot. In some embodiments,
the locations of different sub-bands are in different positions, as
described above.

[0142]FIG. 7c illustrates an example spectrum for each of two time slots
as described above with regard to FIGS. 7a and 7b. FIG. 7c illustrates a
first time slot T1 in which DL communications occur on frequency band F1,
which includes Sub-band R-UE, Sub-band B and Sub-band R-B and a second
time slot T2 in which UL communications occur on frequency band 71, which
includes Sub-band R-UE, Sub-band B and Sub-band R-B.

[0143] While a single base station, single relay station and single mobile
station are illustrated in FIGS. 6a, 6b, 7a and 7b, it is to be
understood that a network may have multiple base stations, each base
station communicating with one or more relay stations and possibly one or
more one hop away mobile stations, each relay station communicating with
one or more mobile station and possibly one or more second relay stations
that may communicate with mobile stations.

[0144] In some embodiments, Sub-band R-B and Sub-band R-UE can be re-used
by the base station and relay station to further improve the spectrum
efficiency.

[0145] A method for use by a relay station will now be described with
regard to FIG. 8. A first step 8-1 of the method involves for a
communication link between a base station and at least one relay station
with which the base station is communicating, allocating a first
frequency sub-band. A second Step 8-2 of the method involves for a
communication link between the base station and a first subset of one or
more mobile stations with which the base station is communicating,
allocating a second frequency sub-band. A third step 8-3 of the method
involves for a communication link between the at least one relay station
and a second subset of one or more mobile stations with which the at
least one relay is communicating, allocating a third frequency sub-band.
A fourth step 8-4 of the method involves the at least one relay station
performing at least one of: receiving signals on the first frequency
sub-band and transmitting signals on the third frequency sub-band
simultaneously; and transmitting signals on the first frequency sub-band
and receiving signals on the third frequency sub-band simultaneously. The
first, second and third frequency sub-bands are aggregate non-overlapping
sub-bands that collectively provide increased bandwidth.

[0146] In some embodiments, one or more of the first, second and third
frequency sub-bands are first, second or third carrier frequencies,
respectively. In some embodiments, one or more of the first, second or
third carrier frequencies are non-contiguous within the aggregate
increased bandwidth.

[0147] In some embodiments, the first, second and third frequency
sub-bands are contiguous sub-bands within a within the aggregate
increased bandwidth.

[0148] In some embodiments, at least one of the first and third sub-bands
is a dedicated sub-band. In some embodiments, at least one of the first
and third sub-bands is dynamically assigned to a different sub-band than
the dedicated first or third sub-band, respectively. In some embodiments,
the bandwidth of at least one of the first, second and third sub-bands is
variable in size and the bandwidth is dynamically assigned.

[0149] In a FDD implementation, allocating the first frequency sub-band
comprises allocating in a down link (DL) frequency band a first DL
frequency sub-band and in an up link (UL) frequency band a first UL
frequency sub-band; allocating the second frequency sub-band comprises
allocating in the DL frequency band a second DL frequency sub-band and in
the UL frequency band a second UL frequency sub-band; allocating the
third frequency sub-band comprises allocating in the DL frequency band a
third DL frequency sub-band and in the UL frequency band a third UL
frequency sub-band; the at least one relay station performing one or more
of receiving signals on the first DL frequency sub-band, transmitting
signals on the third DL frequency sub-band, transmitting signals on the
first UL frequency sub-band and receiving signals on the third UL
frequency sub-band simultaneously in a same time slot.

[0150] In a TDD implementation, in a first time slot for down link (DL)
communications, allocating in a frequency band the first frequency
sub-band, the second frequency sub-band and the third frequency sub-band;
in a second time slot for up link (UL) communications, allocating in the
frequency band the first frequency sub-band, the second frequency
sub-band and the third frequency sub-band; the at least one relay station
performing; receiving signals on the first frequency sub-band and
transmitting signals on the third frequency sub-band simultaneously
during the first time slot; and transmitting signals on the first
frequency sub-band and receiving signals on the third frequency sub-band
simultaneously in the second time slot.

[0151] A similar method to that described above may be implemented by the
base station with which the relay station is communicating. In some
embodiments, the base station is responsible for allocating the sub-bands
and/or carriers, for use in DL and UL communications between the base
station and relay station, between the base station and one hop away
mobile stations, between the relay station and additional relay stations
two hops away from the base station and between the relay station and
mobile stations with which the relay station communicates. Once the base
station has allocated the sub-bands and/or carriers, the base station
notifies the relay station so that the relay station knows which
sub-bands and/or carriers it is transmitting/receiving on. The relay
station may further forward this information along to mobile stations
with which the relay station communicates. The base station may then be
responsible for dynamically assigning different sub-bands and/or carriers
as necessary, for example in the case of legacy mobiles, as described
above.

[0152] Furthermore, a system including at least one base station, at least
relay station and at least one mobile station, may collectively perform
the method described above.

Tx/Rx Guard Gap Reduction

[0153] In some embodiments of the invention, transmission power
distribution control is applied to reduce the interference between
transmissions and receptions in the relay station.

[0154]FIG. 9 illustrates an example of an aggregated spectrum 900 used in
conjunction with a relay station in which Carrier R-E 910 and Carrier
R-UE 920 are separated by a guard band 930. Such a guard band may include
one or more carriers that are not being used, or one or more carriers
that may be used for some type of communication signal. For example, as
described above in FIG. 2, at least one carrier between Carrier R-B 910
and carrier R-UE 920 may be used for communications between the base
station and one hop away mobile station.

[0155] In some embodiments, controlling the transmit power and the
bandwidth of communications from the base station may enable the guard
band to be reduced. Two formats of signal are illustrated as being
transmitted on Carrier R-B, a narrow band, higher peak power signal,
indicated at 940, and a wider band, lower peak power signal, indicated at
950. Signal 940 has a higher peak power and narrower bandwidth than
signal 950. The narrower bandwidth of signal 940 results in a lower power
in an area of guard band 930 than that of signal 950. For example, at a
location in the spectrum indicated at 960, the power of the narrow band
signal 940 is half the level of the wideband signal 950, with respect to
the base level of the two signals. Therefore, since the narrow band
signal 940 has a lower power at a same location in the guard band 930, in
comparison to the wide band signal 950, the two carrier signals, Carrier
R-B 810 and Carrier R--UE 820, could use a smaller guard band, for a
similar level of transmit/receive interference reduction control.

[0156] In some embodiments, the narrow band signal with higher power may
be useful when the desired target node, i.e. the relay station is far
away from the base station. In some embodiments, the wide band signal
with lower power may be useful when the desired target node, i.e. the
relay station is in close proximity to the base station. However, the
narrow band signal with higher power may be used when the desired target
node, i.e. the relay station is in close proximity to the base station,
but a reduced guard band is desired between the carriers used by the
relay station for communicating with the base station and mobile
stations.

[0157] In some embodiments, the relay station may use similar transmission
power distribution control for transmissions to the base station, mobile
stations, and other relay stations.

Description of Example Components of a Communication System

[0158] With reference to FIG. 10, an example of a base station 14 is
illustrated. The base station 14 generally includes a control system 20,
a baseband processor 22, transmit circuitry 24, receive circuitry 26,
multiple antennas 28, and a network interface 30. The receive circuitry
26 receives radio frequency signals bearing information from one or more
remote transmitters provided by mobile terminals 16 (illustrated in FIG.
11) and relay stations 15 (illustrated in FIG. 12). A low noise amplifier
and a filter (not shown) may cooperate to amplify and remove broadband
interference from the signal for processing. Downconversion and
digitization circuitry (not shown) will then downconvert the filtered,
received signal to an intermediate or baseband frequency signal, which is
then digitized into one or more digital streams.

[0159] The baseband processor 22 processes the digitized received signal
to extract the information or data bits conveyed in the received signal.
This processing typically comprises demodulation, decoding, and error
correction operations. As such, the baseband processor 22 is generally
implemented in one or more digital signal processors (DSPs) or
application-specific integrated circuits (ASICs). The received
information is then sent across a wireless network via the network
interface 30 or transmitted to another mobile terminal 16 serviced by the
base station 14, either directly or with the assistance of a relay 15.

[0160] On the transmit side, the baseband processor 22 receives digitized
data, which may represent voice, data, or control information, from the
network interface 30 under the control of control system 20, and encodes
the data for transmission. The encoded data is output to the transmit
circuitry 24, where it is modulated by one or more carrier signals having
a desired transmit frequency or frequencies. A power amplifier (not
shown) will amplify the modulated carrier signals to a level appropriate
for transmission, and deliver the modulated carrier signals to the
antennas 28 through a matching network (not shown). Modulation and
processing details are described in greater detail below.

[0161] with reference to FIG. 11, an example of a mobile terminal 16 is
illustrated. Similarly to the base station 14, the mobile terminal 16
will include a control system 32, a baseband processor 34, transmit
circuitry 36, receive circuitry 38, multiple antennas 40, and user
interface circuitry 42. The receive circuitry 38 receives radio frequency
signals bearing information from one or more base stations 14 and relays
15. A low noise amplifier and a filter (not shown) may cooperate to
amplify and remove broadband interference from the signal for processing.
Downconversion and digitization circuitry (not shown) will then
downconvert the filtered, received signal to an intermediate or baseband
frequency signal, which is then digitized into one or more digital
streams.

[0162] The baseband processor 34 processes the digitized received signal
to extract the information or data bits conveyed in the received signal.
This processing typically comprises demodulation, decoding, and error
correction operations. The baseband processor 34 is generally implemented
in one or more digital signal processors (DSPs) and application specific
integrated circuits (ASICs).

[0163] For transmission, the baseband processor 34 receives digitized
data, which may represent voice, video, data, or control information,
from the control system 32, which it encodes for transmission. The
encoded data is output to the transmit circuitry 36, where it is used by
a modulator to modulate one or more carrier signals that is at a desired
transmit frequency or frequencies. A power amplifier (not shown) will
amplify the modulated carrier signals to a level appropriate for
transmission, and deliver the modulated carrier signal to the antennas 40
through a matching network (not shown), Various modulation and processing
techniques available to those skilled in the art are used for signal
transmission between the mobile terminal and the base station, either
directly or via the relay station.

[0164] In OFDM modulation, the transmission band is divided into multiple,
orthogonal carrier waves. Each carrier wave is modulated according to the
digital data to be transmitted. Because OFDM divides the transmission
band into multiple carriers, the bandwidth per carrier decreases and the
modulation time per carrier increases. Since the multiple carriers are
transmitted in parallel, the transmission rate for the digital data, or
symbols, on any given carrier is lower than when a single carrier is
used.

[0165] OFDM modulation utilizes the performance of an Inverse Fast Fourier
Transform (IFFT) on the information to be transmitted. For demodulation,
the performance of a Fast Fourier Transform (FFT) on the received signal
recovers the transmitted information. In practice, the IFFT and FFT are
provided by digital signal processing carrying out an Inverse Discrete
Fourier Transform (IDFT) and Discrete Fourier Transform (DFT),
respectively. Accordingly, the characterizing feature of OFDM modulation
is that orthogonal carrier waves are generated for multiple bands within
a transmission channel. The modulated signals are digital signals having
a relatively low transmission rate and capable of staying within their
respective bands. The individual carrier waves are not modulated directly
by the digital signals. Instead, all carrier waves are modulated at once
by IFFT processing.

[0166] In operation, OFDM is preferably used for at least downlink
transmission from the base stations 14 to the mobile terminals 16. Each
base station 14 is equipped with "n" transmit antennas 28 (n>=1), and
each mobile terminal 16 is equipped with "m" receive antennas 40
(m>=1). Notably, the respective antennas can be used for reception and
transmission using appropriate duplexers or switches and are so labelled
only for clarity.

[0167] When relay stations 15 are used, OFDM is preferably used for
downlink transmission from the base stations 14 to the relays 15 and from
relay stations 15 to the mobile terminals 16.

[0168] With reference to FIG. 12, an example of a relay station 15 is
illustrated. Similarly to the base station 14, and the mobile terminal
16, the relay station 15 will include a control system 132, a baseband
processor 134, transmit circuitry 136, receive circuitry 138, multiple
antennas 130, and relay circuitry 142. The relay circuitry 142 enables
the relay 14 to assist in communications between a base station 16 and
mobile terminals 16. The receive circuitry 138 receives radio frequency
signals bearing information from one or more base stations 14 and mobile
terminals 16. A low noise amplifier and a filter (not shown) may
cooperate to amplify and remove broadband interference from the signal
for processing. Downconversion and digitization circuitry (not shown)
will then downconvert the filtered, received signal to an intermediate or
baseband frequency signal, which is then digitized into one or more
digital streams.

[0169] The baseband processor 134 processes the digitized received signal
to extract the information or data bits conveyed in the received signal.
This processing typically comprises demodulation, decoding, and error
correction operations. The baseband processor 134 is generally
implemented in one or more digital signal processors (DSPs) and
application specific integrated circuits (ASICs).

[0170] For transmission, the baseband processor 134 receives digitized
data, which may represent voice, video, data, or control information,
from the control system 132, which it encodes for transmission. The
encoded data is output to the transmit circuitry 136, where it is used by
a modulator to modulate one or more carrier signals that is at a desired
transmit frequency or frequencies. A power amplifier (not shown) will
amplify the modulated carrier signals to a level appropriate for
transmission, and deliver the modulated carrier signal to the antennas
130 through a matching network (not shown). Various modulation and
processing techniques available to those skilled in the art are used for
signal transmission between the mobile terminal and the base station,
either directly or indirectly via a relay station, as described above.

[0171] With reference to FIG. 13, a logical OFDM transmission architecture
will be described. Initially, the base station controller 10 will send
data to be transmitted to various mobile terminals 16 to the base station
14, either directly or with the assistance of a relay station 15. The
base station 14 may use the channel quality indicators (CQIs) associated
with the mobile terminals to schedule the data for transmission as well
as select appropriate coding and modulation for transmitting the
scheduled data. The CQIs may be directly from the mobile terminals 16 or
determined at the base station 14 based on information provided by the
mobile terminals 16. In either case, the CQI for each mobile terminal 16
is a function of the degree to which the channel amplitude (or response)
varies across the OFDM frequency band.

[0172] Scheduled data 44, which is a stream of bits, is scrambled in a
manner reducing the peak-to-average power ratio associated with the data
using data scrambling logic 46. A cyclic redundancy check (CRC) for the
scrambled data is determined and appended to the scrambled data using CRC
adding logic 48. Next, channel coding is performed using channel encoder
logic 50 to effectively add redundancy to the data to facilitate recovery
and error correction at the mobile terminal 16. Again, the channel coding
for a particular mobile terminal 16 is based on the CQI. In some
implementations, the channel encoder logic 50 uses known Turbo encoding
techniques. The encoded data is then processed by rate matching logic 52
to compensate for the data expansion associated with encoding.

[0173] Bit interleaver logic 54 systematically reorders the bits in the
encoded data to minimize the loss of consecutive data bits. The resultant
data bits are systematically mapped into corresponding symbols depending
on the chosen baseband modulation by mapping logic 56. Preferably,
Quadrature Amplitude Modulation (QAM) or Quadrature Phase Shift Key
(QPSK) modulation is used. The degree of modulation is preferably chosen
based on the CQI for the particular mobile terminal. The symbols may be
systematically reordered to further bolster the immunity of the
transmitted signal to periodic data loss caused by frequency selective
fading using symbol interleaves logic 58.

[0174] At this point, groups of bits have been mapped into symbols
representing locations in an amplitude and phase constellation. When
spatial diversity is desired, blocks of symbols are then processed by
space-time block code (STC) encoder logic 60, which modifies the symbols
in a fashion making the transmitted signals more resistant to
interference and more readily decoded at a mobile terminal 16. The STC
encoder logic 60 will process the incoming symbols and provide "n"
outputs corresponding to the number of transmit antennas 28 for the base
station 14. The control system 20 and/or baseband processor 22 as
described above with respect to FIG. 13 will provide a mapping control
signal to control STC encoding. At this point, assume the symbols for the
"n" outputs are representative of the data to be transmitted and capable
of being recovered by the mobile terminal 16.

[0175] For the present example, assume the base station 14 has two
antennas 28 (n=2) and the STC encoder logic 60 provides two output
streams of symbols. Accordingly, each of the symbol streams output by the
STC encoder logic 60 is sent to a corresponding IFFT processor 62,
illustrated separately for ease of understanding. Those skilled in the
art will recognize that one or more processors may be used to provide
such digital signal processing, alone or in combination with other
processing described herein. The IFFT processors 62 will preferably
operate on the respective symbols to provide an inverse Fourier
Transform. The output of the IFFT processors 62 provides symbols in the
time domain. The time domain symbols are grouped into frames, which are
associated with a prefix by prefix insertion logic 64. Each of the
resultant signals is up-converted in the digital domain to an
intermediate frequency and converted to an analog signal via the
corresponding digital up-conversion (DUC) and digital-to-analog (D/A)
conversion circuitry 66. The resultant (analog) signals are then
simultaneously modulated at the desired RF frequency, amplified, and
transmitted via the RF circuitry 68 and antennas 28. Notably, pilot
signals known by the intended mobile terminal 16 are scattered among the
sub-carriers. The mobile terminal 16, which is discussed in detail below,
will use the pilot signals for channel estimation.

[0176] Reference is now made to FIG. 14 to illustrate reception of the
transmitted signals by a mobile terminal 16, either directly from base
station 14 or with the assistance of relay 15. Upon arrival of the
transmitted signals at each of the antennas 40 of the mobile terminal 16,
the respective signals are demodulated and amplified by corresponding RF
circuitry 70. For the sake of conciseness and clarity, only one of the
two receive paths is described and illustrated in detail.
Analog-to-digital (AID) converter and down-conversion circuitry 72
digitizes and downconverts the analog signal for digital processing. The
resultant digitized signal may be used by automatic gain control
circuitry (AGC) 74 to control the gain of the amplifiers in the RF
circuitry 70 based on the received signal level.

[0177] Initially, the digitized signal is provided to synchronization
logic 76, which includes coarse synchronization logic 78, which buffers
several OFDM symbols and calculates an auto-correlation between the two
successive OFDM symbols. A resultant time index corresponding to the
maximum 10 of the correlation result determines a fine synchronization
search window, which is used by fine synchronization logic 80 to
determine a precise framing starting position based on the headers. The
output of the fine synchronization logic 80 facilitates frame acquisition
by frame alignment logic 84. Proper framing alignment is important so
that subsequent FFT processing provides an accurate conversion from the
time domain to the frequency domain. The fine synchronization algorithm
is based on the correlation between the received pilot signals carried by
the headers and a local copy of the known pilot data. Once frame
alignment acquisition occurs, the prefix of the OFDM symbol is removed
with prefix removal logic 86 and resultant samples are sent to frequency
offset correction logic 88, which compensates for the system frequency
offset caused by the unmatched local oscillators in the transmitter and
the receiver. Preferably, the synchronization logic 76 includes frequency
offset and clock estimation logic 82, which is based on the headers to
help estimate such effects on the transmitted signal and provide those
estimations to the correction logic 88 to properly process OFDM symbols.

[0178] At this point, the OFDM symbols in the time domain are ready for
conversion to the frequency domain using FFT processing logic 90. The
results are frequency domain symbols, which are sent to processing logic
92. The processing logic 92 extracts the scattered pilot signal using
scattered pilot extraction logic 94, determines a channel estimate based
on the extracted pilot signal using channel estimation logic 96, and
provides channel responses for all sub-carriers using channel
reconstruction logic 98. In order to determine a channel response for
each of the sub-carriers, the pilot signal is essentially multiple pilot
symbols that are scattered among the data symbols throughout the OFDM
sub-carriers in a known pattern in both time and frequency. Continuing
with FIG. 14, the processing logic compares the received pilot symbols
with the pilot symbols that are expected in certain sub-carriers at
certain times to determine a channel response for the sub-carriers in
which pilot symbols were transmitted. The results are interpolated to
estimate a channel response for most, if not all, of the remaining
sub-carriers for which pilot symbols were not provided. The actual and
interpolated channel responses are used to estimate an overall channel
response, which includes the channel responses for most, if not all, of
the sub-carriers in the OFDM channel.

[0179] The frequency domain symbols and channel reconstruction
information, which are derived from the channel responses for each
receive path are provided to an STC decoder 100, which provides STC
decoding on both received paths to recover the transmitted symbols. The
channel reconstruction information provides equalization information to
the STC decoder 100 sufficient to remove the effects of the transmission
channel when processing the respective frequency domain symbols.

[0180] The recovered symbols are placed back in order using symbol
de-interleaver logic 102, which corresponds to the symbol interleaver
logic 58 of the transmitter. The de-interleaved symbols are then
demodulated or de-mapped to a corresponding bitstream using de-mapping
logic 104. The bits are then de-interleaved using bit de-interleaver
logic 106, which corresponds to the bit interleaver logic 54 of the
transmitter architecture. The de-interleaved bits are then processed by
rate de-matching logic 108 and presented to channel decoder logic 110 to
recover the initially scrambled data and the CRC checksum. Accordingly,
CRC logic 112 removes the CRC checksum, checks the scrambled data in
traditional fashion, and provides it to the de-scrambling logic 114 for
de-scrambling using the known base station de-scrambling code to recover
the originally transmitted data 116.

[0181] In parallel to recovering the data 116, a CQI, or at least
information sufficient to create a CQI at the base station 14, is
determined and transmitted to the base station 14. As noted above, the
CQI may be a function of the carrier-to-interference ratio (CR), as well
as the degree to which the channel response varies across the various
sub-carriers in the OFDM frequency band. For this embodiment, the channel
gain for each sub-carrier in the OFDM frequency band being used to
transmit information is compared relative to one another to determine the
degree to which the channel gain varies across the OFDM frequency band.
Although numerous techniques are available to measure the degree of
variation, one technique is to calculate the standard deviation of the
channel gain for each sub-carrier throughout the OFDM frequency band
being used to transmit data.

[0182] Referring to FIGS. 7(a) and 7(b), examples of an SC-FDMA
transmitter and receiver for single-in single-out (SISO) configuration
are respectively illustrated in accordance with one embodiment of the
present application. In SISO, mobile stations transmit on one antenna and
base stations and/or relay stations receive on one antenna. FIGS. 7(a)
and 7(b) illustrate the basic signal processing steps needed at the
transmitter and receiver for an LTE SC-FDMA uplink. In some embodiments,
SC-FDMA (Single-Carrier Frequency Division Multiple Access) is used.
SC-FDMA is a modulation and multiple access scheme introduced for the
uplink of 3GPP Long Term Evolution (LTE) broadband wireless fourth
generation (4G) air interface standards, and the like. SC-FDMA can be
viewed as a DFT pre-coded OFDMA scheme, or, it can be viewed as a single
carrier (SC) multiple access scheme. There are several similarities in
the overall transceiver processing of SC-FDMA and OFDMA. Those common
aspects between OFDMA and SC-FDMA are illustrated in the OFDMA TRANSMIT
CIRCUITRY and OFDMA RECEIVE CIRCUITRY, as they would be obvious to a
person having ordinary skill in the art in view of the present
specification. SC-FDMA is distinctly different from OFDMA because of the
DFT pre-coding of the modulated symbols, and the corresponding IDFT of
the demodulated symbols. Because of this pre-coding, the SC-FDMA
sub-carriers are not independently modulated as in the case of the OFDMA
sub-carriers. As a result, PAPR of SCFDMA signal is lower than the PAPR
of OFDMA signal. Lower PAPR greatly benefits the mobile terminal in terms
of transmit power efficiency.

[0183] FIGS. 1 and 10 to 15(a) and 15(b) provide one specific example of a
communication system that could be used to implement embodiments of the
application. It is to be understood that embodiments of the application
can be implemented with communications systems having architectures that
are different than the specific example, but that operate in a manner
consistent with the implementation of the embodiments as described
herein.

[0184] Numerous modifications and variations of the present invention are
possible in light of the above teachings. It is therefore to be
understood that within the scope of the appended claims, the invention
may be practised otherwise than as specifically described herein.